57 lines
1.4 KiB
C++
Executable File
57 lines
1.4 KiB
C++
Executable File
/*
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Floppy Emu, copyright 2013 Steve Chamberlin, "Big Mess o' Wires". All rights reserved.
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Floppy Emu is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported
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license. (CC BY-NC 3.0) The terms of the license may be viewed at
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http://creativecommons.org/licenses/by-nc/3.0/
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Based on a work at http://www.bigmessowires.com/macintosh-floppy-emu/
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Permissions beyond the scope of this license may be available at www.bigmessowires.com
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or from mailto:steve@bigmessowires.com.
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*/
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#include <avr/interrupt.h>
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#include <util/atomic.h>
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#include "millitimer.h"
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static uint32_t milliCount;
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void millitimerInit()
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{
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TCCR0A = 0; // normal counter mode
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TCCR0B = (1<<CS01) | (1<<CS00); // use oscillator/64: 4 microseconds at 16 MHz
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TIFR0 = (1 << TOV0); // clear the timer 0 interrupt flags
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// don't enable the interrupt yet
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//TIMSK0 = (1 << TOIE0); // enable timer 0 overflow interrupt
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}
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void millitimerOn()
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{
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TIMSK0 = (1 << TOIE0); // enable timer 0 overflow interrupt
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}
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void millitimerOff()
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{
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TIMSK0 = 0;
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}
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ISR(TIMER0_OVF_vect)
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{
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// timer overflows every 256 * 4 microseconds = 1.024 milliseconds
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milliCount++;
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}
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uint32_t millis()
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{
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// What happens if the millitimer interrupt occurs in the middle of this function? A bad count could be returned
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uint32_t returnValue;
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ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
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{
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returnValue = milliCount;
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}
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return returnValue;
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} |